在Python中将标准输出重定向到文件?

如何在Python中将标准输出重定向到任意文件?

When a long-running Python script (e.g, web application) is started from within the ssh session and backgounded, and the ssh session is closed, the application will raise IOError and fail the moment it tries to write to stdout. I needed to find a way to make the application and modules output to a file rather than stdout to prevent failure due to IOError. Currently, I employ nohup to redirect output to a file, and that gets the job done, but I was wondering if there was a way to do it without using nohup, out of curiosity.

我已经试过了。Stdout = open('somefile'， 'w')，但这似乎并没有阻止一些外部模块仍然输出到终端(或者sys. exe)。Stdout =…Line根本没有开火)。我知道它应该在我测试过的更简单的脚本上工作，但我还没有时间在web应用程序上进行测试。

当前回答

以下是Yuda Prawira的回答:

实现flush()和所有文件属性将其编写为上下文管理器也捕获stderr

import contextlib, sys

@contextlib.contextmanager
def log_print(file):
    # capture all outputs to a log file while still printing it
    class Logger:
        def __init__(self, file):
            self.terminal = sys.stdout
            self.log = file

        def write(self, message):
            self.terminal.write(message)
            self.log.write(message)

        def __getattr__(self, attr):
            return getattr(self.terminal, attr)

    logger = Logger(file)

    _stdout = sys.stdout
    _stderr = sys.stderr
    sys.stdout = logger
    sys.stderr = logger
    try:
        yield logger.log
    finally:
        sys.stdout = _stdout
        sys.stderr = _stderr


with log_print(open('mylogfile.log', 'w')):
    print('hello world')
    print('hello world on stderr', file=sys.stderr)

# you can capture the output to a string with:
# with log_print(io.StringIO()) as log:
#   ....
#   print('[captured output]', log.getvalue())

2018-02-19 16:48:10

其他回答

引用自PEP 343 -“with”语句(添加了import语句):

临时重定向标准输出:

import sys
from contextlib import contextmanager
@contextmanager
def stdout_redirected(new_stdout):
    save_stdout = sys.stdout
    sys.stdout = new_stdout
    try:
        yield None
    finally:
        sys.stdout = save_stdout

用途如下:

with open(filename, "w") as f:
    with stdout_redirected(f):
        print "Hello world"

当然，这不是线程安全的，但手动执行相同的操作也不是。在单线程程序(例如脚本)中，这是一种流行的做事方式。

2013-02-05 12:09:49

其他答案不包括您希望分叉进程共享您的新标准输出的情况。

做那件事:

from os import open, close, dup, O_WRONLY

old = dup(1)
close(1)
open("file", O_WRONLY) # should open on 1

..... do stuff and then restore

close(1)
dup(old) # should dup to 1
close(old) # get rid of left overs

2012-07-24 14:24:53

你可以尝试更好的方法

import sys

class Logger(object):
    def __init__(self, filename="Default.log"):
        self.terminal = sys.stdout
        self.log = open(filename, "a")

    def write(self, message):
        self.terminal.write(message)
        self.log.write(message)

sys.stdout = Logger("yourlogfilename.txt")
print "Hello world !" # this is should be saved in yourlogfilename.txt

2011-05-06 20:49:48

如果您想在Python脚本中进行重定向，请设置sys. exe。对文件对象的Stdout是有用的:

# for python3
import sys
with open('file', 'w') as sys.stdout:
    print('test')

一个更常见的方法是在执行时使用shell重定向(在Windows和Linux上相同):

$ python3 foo.py > file

2011-01-13 00:53:28

以下是Yuda Prawira的回答:

实现flush()和所有文件属性将其编写为上下文管理器也捕获stderr

import contextlib, sys

@contextlib.contextmanager
def log_print(file):
    # capture all outputs to a log file while still printing it
    class Logger:
        def __init__(self, file):
            self.terminal = sys.stdout
            self.log = file

        def write(self, message):
            self.terminal.write(message)
            self.log.write(message)

        def __getattr__(self, attr):
            return getattr(self.terminal, attr)

    logger = Logger(file)

    _stdout = sys.stdout
    _stderr = sys.stderr
    sys.stdout = logger
    sys.stderr = logger
    try:
        yield logger.log
    finally:
        sys.stdout = _stdout
        sys.stderr = _stderr


with log_print(open('mylogfile.log', 'w')):
    print('hello world')
    print('hello world on stderr', file=sys.stderr)

# you can capture the output to a string with:
# with log_print(io.StringIO()) as log:
#   ....
#   print('[captured output]', log.getvalue())

2018-02-19 16:48:10

在Python中将标准输出重定向到文件?

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